Agricultural applicators are committed to the management of chemical drift and take responsibility on a daily basis for making good decisions in the field.
Aerial services provided by fixed-wing aircraft and helicopters are used to fight forest or grassland fires, feed fish, melt snow and control pests that threaten human health in addition to agricultural functions such as seeding crops or the application of pesticides (herbicides, insecticides, rodenticides, fungicides, bactericide, germicide, microbicide, larvicide, defoliants, and fertilizers to food and fiber crops. In United States agriculture, about one half of the crop production materials applied are delivered to the target by air. Aircrafts can cover large areas very quickly without disturbing either the soil or crops. Aircrafts also can operate when fields are too wet for ground application methods. This is important because some pests and/or diseases can do serious damage in just a few days and also because ground application methods can contribute to soil compaction and/or physically damage the crop.
A 1994 survey by the National Agricultural Aviation Association found that there are approximately 2500 agricultural pilot/operators in the United States who fly approximately 3,000 aircrafts. Each of these aircrafts treated an average of ˜50,000 acres per year, representing a total of roughly 1.5 million acres. Most of the operators who returned the survey expected to expand their enterprises either with larger capacity aircraft or by increasing the hours each aircraft would be operated. All of the operators responding applied liquid materials, with herbicides representing 78% and fertilizers the remaining 22% of the materials applied. Nationwide, over 70% of these operators applied dry materials.
Material that drifts offsite is material that is not applied to the target crop or pest and represents wasted time and wasted material as well as wasted fuel. The drifting offsite results in increased costs for both the farmer and applicator and subsequently to the public and consumer. Materials such as herbicides and defoliants, for example that drift offsite can be a serious financial liability, particularly if surrounding crops suffer actual crop damage or off-label residues become present on the crop that should not have been sprayed. Environmental concerns for air and water quality protection and for animal habitat maintenance and endangered species protection make off-target spray drift an issue of high concern. Drift into/onto protected or particularly sensitive areas present a serious financial liability for the applicator, as well as an environmental issue.
Offsite spray drift is also a concern to the city dweller. As suburban populations spread into formerly rural and agricultural areas, buffer zones and/or no spray zones between populated and agricultural areas will increase in number and in total acreage. The imposition of buffer and no spray zones increases the difficulty for aerial applicators to do their job. The more complaints that are registered and more lawsuits filed, the more likely that additional regulations and/or restrictions on sprayers will be enacted, yet again affecting the cost of food.
The majority of agricultural materials are applied as a liquid solution from a nozzle-atomizer unit, also called a nozzle injector. The nozzle-atomizer must perform two functions. First, it must discharge the solution at a controlled and metered rate to provide appropriate coverage and accurate dosage for the material being applied and the crop/pest being treated/targeted. Second, the nozzle-atomizer must break the solution into appropriately sized drops for dispersal onto the target. Most nozzle-atomizers in use on agricultural sprayers produce a simultaneous range of drop sizes approximating a Gaussian or bell curve distribution range, which may be somewhat skewed towards smaller drops. It has not been determined that the production of a single-size drop would produce the most desirable coverage of plant surfaces, but it is widely understood that narrowed spectrum, which eliminates both the smallest and largest drops in the range, would be a desirable improvement in nozzle-atomizer [injector] design. By concentrating the drop size in a narrower range, the smallest, most drift-prone (fines) and the largest drops that produce poor coverage would be reduced significantly. Fines constitute that portion of the total spray that is likely to drift off and away from the intended target due to the smallness of the size of the drops of sprayed liquid.
Most nozzles utilize traditional designs, hydraulic pressure, fan, cone dispersion, solid stream, or rotary screen type design factors. These nozzles, when used on an aircraft, be it fixed wing or helicopter, release the spray solution into the airstream and utilize both the nozzle and air shear for atomization. Applicant, who has been in the field of aerial spraying for 30 years, has seen minimal advances in nozzle design with respect to the reduction of fines for spray drift control for aircraft over the last 15–20 years.
In most situations, aerial applicators have simply been using “off-the-shelf” nozzles, originally designed for ground applications and not specifically for aircrafts. Newer, more advanced nozzles are more convenient in actual use and can be changed more easily. Applicators have been creative in combining nozzles, nozzle orientation, spray pressure, and also have paid attention to environmental conditions, to obtain satisfactory application patterns to minimize offsite drift.
Ground application is slow and costly in man hours, particularly on large acreage, and is also very weather and condition dependent. Ground rigs simply cannot operate in fields when they are wet from either rain or irrigation.
Therefore to increase speed of application, aerial methods have been employed for many years. Early air applications were carried out by biplanes applying materials in dust form, DDT applicators became known as “crop dusters”. Compared to ground-based spray methods, both fixed-wing aircraft and helicopters are much faster. Both helicopters and aircrafts are cost-effective in large-acreage or “narrow window” situations. Unfortunately, as air speed increases, so does the percentage of driftable fine droplets <200μ. Air shear “shatters” the droplets into “fines” and as air speed increases, so does turbulence, thus increasing the percentage of fines. Propeller turbulence (prop wash) in fixed-wing aircraft creates additional problems.
There is a need therefore to develop a method of dispensing agricultural materials in a dependable manner from a fixed-wing aircraft that will produce an appropriate size range of droplets, with a reduced percentage of fines <200μ, (driftable fines). The achieving of this goal will greatly reduce the potential for offsite spray drift.
There is also a need for an apparatus that be used to deliver various chemical agents to the target site which will minimize the formation of fines, that is drops of liquid that are smaller than 200 micron units.
These and other problems associated with on target confined delivery are addressed by this invention which employs a venturi chamber having two sections, a left section and a right section, each of which section is divided into two segments. The two segments of each section have mirror image upper and lower walls. The outer segment has a convex radius upper wall and a concave radius lower wall, while the inner segment has a convex radius upper wall and a concave radius lower wall. Each segment's upper and lower wall are substantially and same radius. The sidewalls of each section may be flat, or arcuate or other convenient shape, so long as uniform throughout the apparatus.
The invention accordingly comprises the device possessing the features, properties, the selection of components which are amplified in the following detailed disclosure, and the scope of the application of which will be indicated in the appended claims. For a fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings.